20. Calcium

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Calcium is the 20th element on the periodic table. It has 20 protons and 20 neutrons in the nucleus, giving it a mass of 40 amu, and it has 20 electrons enveloping the nucleus.

Electron Shell

Calcium has the same electron configuration as magnesium, but with three full shells within that have the identical configuration to argon. Being one shell larger than magnesium, calcium’s valence electrons are less well bound, causing it to be more reactive than magnesium, but much less so than potassium.

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As we saw in the case of argon, the 3rd shell orbitals are more like spherical tetrahedra, and the 4th shell is a di-electron in a spherical s-orbital. These orbitals represent phase-locked, resonant, coherent, harmonic, stationary waves.

Ion formation

Calcium will give up its valence electrons in an ionic interaction in order to reach the stability of the 3s23p6 noble gas configuration of argon, which is a multi-di-electron state with three concentric full shells. That is why calcium forms a 2+ ionic state.

Neutral calcium (Ca) atom (L) compared to the much smaller calcium (Ca2+) ion (R)

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OTHER GROUP II ELEMENTS: Beryllium, Magnesium, Calcium, Strontium, Barium

19. Potassium

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Potassium is the 19th element on the periodic table. It has 19 protons and 20 neutrons in the nucleus, giving it a mass of 39 amu, and it has 19 electrons enveloping the nucleus.

Electron Shell

Potassium has the same electron configuration as sodium, but with three full shells within that have the identical configuration to argon. Being one shell larger than sodium, potassium has a lower ionization energy and is therefore more reactive.

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As we saw in the case of argon, the 3rd shell orbitals are more like spherical tetrahedra, and the 4th shell is a single electron in a spherical s-orbital. These orbitals represent phase-locked, resonant, coherent, harmonic, stationary waves.

Ion formation

With a lower ionization energy, potassium will give up its valence electron more eagerly than sodium in an ionic interaction, in order to reach the stability of the 3s23p6 noble gas configuration of argon, which is a multi-di-electron state with three concentric full shells. That is why potassium forms a 1+ ionic state so violently.

Neutral potassium (K) atom (L) compared to the much smaller potassium (K+) ion (R). (Only the 3 outer shells are depicted here.)

Pure potassium metal reacts explosively when placed in water as it donates its valence electron to oxygen. The heat of this reaction ignites the hydrogen gas that is also produced from the water. Potassium burns with a purple flame and throws purple sparks. It is used to create this same effect and color in fireworks. A fun video showing potassium metal and its reactivity can be found HERE.


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OTHER GROUP I ELEMENTS: Lithium, Sodium, Potassium, Rubidium, Cesium

18. Argon

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Argon is the 18th element on the periodic table. It has 18 protons and 22 neutrons in the nucleus, giving it a mass of 40 amu, and it has a full shell of 18 electrons enveloping the nucleus. Its full electron shell causes it not to react with other atoms. It is a gas under normal conditions, and it is called a ‘noble’ gas because of its non-interaction.

Electron Shell

Argon has three full electron shells. With 6 electrons in a 3p orbital, argon is believed to achieve stability with octahedral symmetry, and its 3s electrons can unhybridize and return to their preferred spherical di-electron state. It is proposed in the theory of Sub-Quantum Chemistry, however, that argon is more stable with full shells containing 4 di-electrons in sp3-hybridization (shown below).

This high degree of symmetry, with all electrons paired, renders argon, like helium and neon, unreactive.

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NOTE: The small spheres in the image above simply indicate the directions of maximum electron density. The 3rd shell orbitals themselves are spherical tetrahedra, not spheres. Only s-orbitals are spherical. It is noteworthy that the tetrahedral arrangements in adjacent shells align antiparallel to each other. This places the maximum distance between electron density on adjacent shells in order to minimize electron repulsion.

As in the case of neon, if we consider the tetrahedral full-shell configuration, then argon will have a nested spherical tetrahedral orbital arrangement, the 2nd and 3rd shells each containing four di-electrons (below, right).

Neon’s tetrahedral sp3 orbitals
Argon’s antiparallel nested tetrahedra

Intuitively, this seems more stable as it involves a greater degree of field cancellation than a full p-orbital with a single electron occupying each lobe. The entire shell contains electron density. It will be highest at the center of the face of each orbital (as in the traditional sp3 lobe shapes) and will decrease toward the nodal regions between orbitals, where electron density will be lowest (though not zero). Together, all atomic orbitals constitute a single, phase-locked, resonant, coherent, harmonic, stationary wave.

As mentioned above, the nested tetrahedral shells align in an opposite or antiparallel fashion. The reason this geometry is so stable for electrons is that the region of lowest electron density on one shell lines up with the region of maximum electron density on the adjacent shell, minimizing repulsion. In the diagram (below), the vertex represents where the nodes between orbitals intersect. This is a point of lowest electron density. It lies directly over the center of the face of the orbital beneath it, which is the point of highest electron density in that orbital. This is therefore the lowest energy state that nested tetrahedral shells can achieve.

Argon’s antiparallel nested tetrahedra (left), and with one outer orbital raised (right)

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SEE OTHER NOBLE GASES: Helium, Neon, Argon, Krypton, Xenon

17. Chlorine

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Chlorine is the 17th element on the periodic table. It has 17 protons and (mostly) 18 neutrons in the nucleus, giving it a mass of 35 amu, and it has 17 electrons enveloping the nucleus.

Electron Shell

Chlorine has the same electron configuration as fluorine, just one shell larger. This allows chlorine a broader palette of chemical reactions, given the presence of a d-orbital. Like sulfur, this gives rise to more possible molecular geometries. Chlorine can sustain multiply bonded atoms, but it takes bonding atoms with stronger electronegativity than chlorine in order to draw it into multiple bonds. This limits to list of contenders essentially to oxygen and fluorine, as we see in the chlorate (ClO3) ion. (The wireframe indicates the boundary of the n=3 shell.)

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NOTE: The small spheres in the image above simply indicate the directions of maximum electron density. The 3rd shell orbitals themselves will be more like spherical tetrahedra. The entire shell will be filled with electron density. It will be highest at the center of the face of each orbital (as in the traditional sp3 lobe shapes) and will decrease toward the nodal regions between orbitals, where electron density will be lowest (though not zero). Like argon, chlorine features two nested spherical tetrahedra, the inner 2nd shell comprising 4 di-electrons, the outer 3rd shell comprising 3 di-electrons and 1 single electron. In this case the three orbitals containing the di-electrons (dark pink) will occupy slightly more volume than the one containing an unpaired electron.

Chlorine’s 3sp3 orbitals surrounding the 2sp3 shell

Bonding & ion formation

Chlorine is keen to obtain an extra electron to fill its third shell and it can bond with many atoms on the periodic table. Chlorine can make one or more covalent bonds or gain an electron in ionic interaction in order to reach the stability of the 3s23p6 noble gas configuration of argon, which is a multi-di-electron state with three concentric full shells. That is why chlorine forms a 1– ionic state. The negative ion is larger than its neutral version because electrons now outnumber protons. This results in a lower effective nuclear charge — a lower average attraction by the nucleus on each electron.

Neutral chlorine (Cl) atom (left) compared to the larger chloride (Cl) ion (right)

Salt

When sodium and chlorine interact, sodium gives the electron it wants to lose to chlorine, which is keen to gain it. This forms both atoms into their ions and allows both to achieve full shell configurations. The ions can then stick to each other because of their opposite charges, forming sodium chloride (NaCl) crystals. This process is called ionic bonding, and it occurs between a metal (from the left side of the periodic table) and a non-metal (from the right side). The term “salt” can also be used to apply to any ionic crystal.

Na + Cl prefer to become Na+ + Cl, which can then form NaCl.

Below is another visualization of the formation of sodium chloride from the point of view of electronegativity. The electrons in a bond will always be pulled more strongly towards the atom that is closer to the violet end of the electronegativity spectrum. In this case, there is such a great difference between how strongly they hold their electrons that the chlorine will be able to strip the sodium’s electron completely away. This clarifies why the two ions form, as opposed to them still sharing the electrons (as occurs in water).

The formation of sodium chloride.
The formation of sodium chloride from the point of view of the electronegativity ‘rainbow’ spectrum.

Sodium chloride (NaCl) dissolves in water because the polar H2O molecules and the ions in the crystal attract each other. The water molecules can therefore tug ions off the crystal and still satisfy the ion’s desire to attract their opposite polarity. As each ion leaves the crystal, it becomes hydrated — surrounded by water molecules.

Polar water (H2O) molecules dissolving salt (NaCl).

When the water is allowed to evaporate from the salt solution, the ions become increasingly exposed to one another, and the solid crystals re-form due to electrostatic attraction.

Although the ocean contains many different ions and just about every element on the periodic table (in trace amounts), it is mainly made up of water (H2O) and sodium chloride (NaCl). Of these four elements, the mass of sea water is made up of about 86% oxygen, 11% hydrogen, 1.9% chloride, and 1.1% sodium.


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OTHER GROUP VII HALOGENS: Fluorine, Chlorine, Bromine, Iodine

16. Sulfur

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Sulfur is the 16th element on the periodic table. It has 16 protons and 16 neutrons in the nucleus, giving it a mass of 32 amu, and it has 16 electrons enveloping the nucleus.

Electron Shell

Sulfur has the same electron configuration as oxygen, though as a larger atom and one with a d-orbital into which it can hybridize, sulfur has different properties and can make different molecular geometries than oxygen. (The wireframe indicates the boundary of the n=3 shell.)

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NOTE: The small spheres in the image above simply indicate the directions of maximum electron density. The 3rd shell orbitals themselves will be more like spherical tetrahedra. The entire shell will be filled with electron density. It will be highest at the center of the face of each orbital (as in the traditional sp3 lobe shapes) and will decrease toward the nodal regions between orbitals, where electron density will be lowest (though not zero). Like argon, sulfur features two nested spherical tetrahedra, the inner 2nd shell comprising 4 di-electrons, the outer 3rd shell comprising 2 di-electrons and 2 single electrons. In this case the two orbitals containing the di-electrons (dark pink) will occupy slightly more volume than the two containing an unpaired electron.

Sulfur’s’ 3sp3 orbitals surrounding the 2sp3 shell

Bonding & ion formation

As the structure below indicates, it is common for sulfur to make two bonds. In its natural crystalline form, sulfur forms S8 rings where each sulfur atoms is bonded to two adjacent sulfur atoms. Like oxygen (though not quite as strongly), sulfur is keen to gain two electrons in an ionic interaction in order to reach the stability of the 3s23p6 noble gas configuration of argon, which is a multi-di-electron state with three concentric full shells. That is why sulfur forms a 2– ionic state. The negative ion is much larger than its neutral version because electrons now outnumber protons by two. This results in a lower effective nuclear charge — a lower average attraction by the nucleus on each electron, which expands the size of the electron shell as it is attracted inward with less force.

Neutral sulfur (S) atom (left) compared to the larger sulfide (S2–) ion (right)

But if sulfur is approached by highly electronegative atoms like oxygen or fluorine, they can induce sulfur’s paired valence electrons to uncouple, yielding 6 unpaired electrons available for bonding. This is only possible because the 3rd shell contains a d-orbital. While sulfur does not usually have electrons in its 3d-orbital, the 3rd shell has enough volume to accommodate those orbitals. This allows sulfur to hybridize into those empty d-orbitals and to make up to 6 covalent bonds, as we see in the octahedral SF6 molecule.

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Uses

Sulfur is an abundant element and has a great many uses in nature, biology and chemical technology.

Sulfur is a relatively common atom in protein structures, and it is therefore present throughout the nutrient cycle, as well as being a waste product from the purification of natural gas and oil, which derive from organic materials.

One common form of sulfur in nature is in sulfide molecules, for example hydrogen sulfide (H2S) gas, which is experienced as that notorious ‘rotten egg’ smell. Another is the sulfur dioxide (SO2) gas.

One of the most stable forms of sulfur in nature is the sulfate ion (SO42–). When two electrons are made available by a nearby metal atom, 1 sulfur atom and 4 oxygen atoms can form a symmetrical, tetrahedral arrangement where every atom has a full and symmetrical outer electron shell. Sulfates are a key nutrient in nature.


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15. Phosphorus

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Phosphorus is the 15th element on the periodic table. It has 15 protons and 16 neutrons in the nucleus, giving it a mass of 31 amu, and it has 15 electrons enveloping the nucleus.

Electron Shell

Phosphorus has the same tetrahedral sp3 electron configuration as nitrogen, though, as a larger atom, the chemistry of phosphorus has important differences from that of nitrogen. With an available d-orbital into which to hybridize, phosphorus can achieve a greater variety of molecular geometries than can nitrogen. (The wireframe indicates the boundary of the n=3 shell.)

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NOTE: The small spheres in the image above simply indicate the directions of maximum electron density. The 3rd shell orbitals themselves will be more like spherical tetrahedra. The entire shell will be filled with electron density. It will be highest at the center of the face of each orbital (as in the traditional sp3 lobe shapes) and will decrease toward the nodal regions between orbitals, where electron density will be lowest (though not zero). Like argon, phosphorus features two nested spherical tetrahedra — an inner 2nd shell comprising 4 di-electrons, and the outer 3rd shell comprising 1 di-electron and 3 single electrons. In this case the orbital containing the di-electron (dark pink) will occupy slightly more volume than the three containing an unpaired electron.

Phosphorus’ 3sp3 orbitals surrounding the 2sp3 shell

Bonding & ion formation

Phosphorus is keen to obtain three extra electrons to fill its 3rd shell, though it is not as pressing of an issue for phosphorus as it is for nitrogen since the nuclear charge is lower at the boundary of the larger atom. Phosphorus can make one or more covalent bonds or it can gain three electrons in ionic interaction in order to reach the stability of the 3s23p6 noble gas configuration of argon, which is a multi-di-electron state with three concentric full shells. That is why phosphorus forms a 3– ionic state. The negative ion is much larger than its neutral version because electrons now outnumber protons by three. This results in a much lower effective nuclear charge — a lower average attraction by the nucleus on each electron, which expands the size of the electron shell as it is attracted inward with less force.

Neutral phosphorus (P) atom (left) compared to the larger phosphide (P3–) ion (right)

But if phosphorus is approached by highly electronegative atoms like oxygen or chlorine, they can induce phosphorus’s paired valence electrons to uncouple, yielding 5 unpaired electrons available for bonding. This is only possible because the 3rd shell contains a d-orbital. While phosphorus does not usually have electrons in its 3d-orbital, the 3rd shell has enough volume to accommodate those orbitals. This allows phosphorus to hybridize into that space and to make up to 5 covalent bonds, as we see in the trigonal bipyramidal PCl5 molecule.

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Uses

Since phosphorus has a lower electronegativity than nitrogen, it’s outer electrons are not as well bound. Oxygen will therefore react more easily and strongly with phosphorus than with nitrogen, which is why phosphorus burns (combusts) so readily. It can therefore be used to make matches and incendiary devices.

The most stable form of phosphorus in nature is the phosphate ion (PO43–). When three electrons are made available by nearby metal atoms, 1 phosphorus atom and 4 oxygen atoms can form a symmetrical, tetrahedral arrangement where every atom has a full and symmetrical outer electron shell. Phosphates are a key nutrient in nature. They are commonly found in rocks, from where they are released by erosion, and they also help make up the ‘backbone’ of the DNA molecule in all living things.


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14. Silicon

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Silicon is the 14th element on the periodic table. It has 14 protons and 14 neutrons in the nucleus, giving it a mass of 28 amu, and it has 14 electrons enveloping the nucleus.

Electron Shell

Silicon has the same electron structure as carbon, a hybridized, tetrahedral sp3 configuration. (The wireframe indicates the boundary of the n=3 shell.)

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NOTE: The small spheres in the image above simply indicate the directions of maximum electron density. The 3rd shell orbitals themselves will be more like spherical tetrahedra. The entire shell will be filled with electron density. It will be highest at the center of the face of each orbital (as in the traditional sp3 lobe shapes) and will decrease toward the nodal regions between orbitals, where electron density will be lowest (though not necessarily zero). Like argon, silicon features two nested spherical tetrahedra — an inner 2nd shell comprising 4 di-electrons, and an outer 3rd shell comprising 4 single electrons.

Silicon’s 3sp3 single-electron orbitals surrounding the 2sp3 shell.

Bonding & Properties

Since silicon is a similar though larger atom than carbon, the four degenerate 3rd shell electrons form a less coherent quantum system than they do in carbon. The larger size gives pure silicon different (more semi-metallic) properties than carbon. This is because metals are characterized by the ease with which their electrons can delocalize from the atomic core. The less well-bound they are to the nucleus, the more metallic the nature of the element. This means elements become more metallic as we move down the periodic table (as their ionization energies decrease).

Like carbon silicon can make 4 covalent bonds, and its natural crystal form has the same network covalent structure as diamond. This gives it a high melting point, but not the same strength or hardness as diamond because, being larger, silicon does not bond with itself as strongly as carbon does. We also do not see many organic molecule analogues involving silicon in place of carbon.

Uses

With a lower electronegativity than carbon, oxygen bonds more strongly to silicon than to carbon, making silicates (sand) one of the primary components of earth’s crust. Due to its larger size and less coherent hybridization, along with the presence of a d-orbital in the 3rd shell into which to expand the electron octet, silicon is also capable of octahedral bonding. Silicon-based materials (like silicates) can therefore have more complex crystalline structures than carbon-based oxides.

Since silicon becomes less of an electrical resistor as temperature increases, it is a semiconductor, with important uses in electronics and photovoltaics.


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13. Aluminium

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Aluminium (or Aluminum) is the 13th element on the periodic table. It has 13 protons and 14 neutrons in the nucleus, giving it a mass of 27 amu, and it has 13 electrons enveloping the nucleus.

Electron Shell

Aluminium has interesting chemistry and bears similarities to several different elements. It lies in Group III beneath boron, and with a 3p1 electron configuration, it is similar to boron’s 2p1 configuration. This implies that it will form a triangular (sp2 trigonal planar) geometry. It also has similarities to beryllium and can form bonds of a covalent nature. However, since aluminium is larger than boron, its valence electrons fill a larger volume and are therefore less coherent as a single quantum system. This makes aluminium more metallic in nature than the semi-metallic boron above it. (The wireframe indicates the boundary of the n=3 shell.)

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NOTE: The small spheres in the image above simply indicate the directions of maximum electron density. The 3rd shell orbitals themselves will be more like three longitudinal sections. The entire shell will be filled with electron density. It will be highest at the center of the face of each orbital (as in the traditional sp3 lobe shapes) and will decrease toward the nodal regions between orbitals, where electron density will be lowest (though not zero).

Aluminium’s three 3sp2-orbitals surrounding a full 2nd shell core.

Each of these three hybrid orbitals contains one electron. Like boron’s configuration, this arrangement is symmetrical in the equatorial plane but does not have equivalent symmetry in all directions.

Bonding & ion formation

Aluminum will bond with other metal atoms via a metallic bond, and with non-metals via an ionic bond in which it loses its three valence electrons. It will lose all three at once in order to reach the stability of a full 2nd shell. This is the same electron configuration as the 2s22p6 noble gas configuration of neon — a multi-di-electron state with two concentric full shells. That is why aluminium forms a 3+ ionic state, as in aluminum oxide (Al2O3).

The positive ion is much smaller than the neutral atom because protons now outnumber electrons by three. This results in a much higher effective nuclear charge — a higher average attraction by the nucleus on each electron, which shrinks the size of the electron shell as it is attracted inward with more force.

Neutral aluminium (Al) atom (L) compared to the much smaller Al3+ ion (R)

Some uses & properties

Unlike most other small ions, aluminium ions do not play a biologically useful role. In fact, given their small size and high charge, Al3+ ions are toxic to most organisms.

Aluminium occurs in nature in a bonded, crystalline form. Reducing it to pure metal is done via electrolysis, and uses a large amount of electricity because it requires 3 electrons for every atom of aluminium to turn Al3+ ions into Al0 metal. One of the key uses of this light and strong metal is in the manufacture of aircraft. The first aircraft engine, built by the Wright brothers, was made out of aluminium specifically due to its low density.

When we compare aluminium to boron (B), we see a significant size difference (see below). We also see a significant difference between the magnetic susceptibility of aluminium and the other Group III elements, since aluminium is paramagnetic (χm=+16.5) while the others are diamagnetic. Aluminium’s paramagnetic strength is also very similar to that of sodium (Na) (χm=+16).

Size comparison between boron (left) and aluminium (right)

This might suggest that, in its crystalline metallic state, aluminium also delocalizes only one of its three valence electrons, perhaps allowing the remaining two 3s-electrons to retain some of their preferred spherical di-electron character, stabilizing the 3rd shell with spherical electron density. (This state would not be possible if aluminium were bonding with any other element. Differences in size, effective nuclear charge, and electronegativity would coax the aluminium atom into its normal trivalent configuration.)

If this speculation is correct, it might account for the following observations:

  • aluminium has a magnetic susceptibility value similar to sodium (Na).
  • aluminium has a 2nd ionization energy whose increase is 50% higher than the elements on either side of it (Mg & Si). This suggests that, compared to magnesium and silicon, it is uncharacteristically difficult to remove (or delocalize) aluminium’s 2nd (and 3rd) valence electron.
  • aluminium is a soft metal. It seems reasonable that the presence of a larger 1+ metallic core with a single delocalized electron per atom should result in a lower density metal with weaker metallic bonds than a smaller 3+ metallic core with three delocalized electrons per atom.
  • If aluminium only delocalizes one electron per atom — like copper (Cu), silver (Ag), and gold (Au) — it might account for the fact that aluminium is the 4th best electrical conductor, after silver, copper, and gold.

… and it might have a topology like this:

Speculation on a possible partially-delocalized aluminium valence shell.
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Boron’s diamagnetism (χm=–6.7), on the other hand, would appear to emerge from the fact that it usually makes covalent bonds, in which all of its electrons are paired.


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12. Magnesium

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Magnesium is the 12th element on the periodic table. It has 12 protons and 12 neutrons in the nucleus, giving it a mass of 24 amu, and it has 12 electrons enveloping the nucleus.

Electron Shell

Magnesium has a di-electron making up its 3rd shell, with two full core shells within that have the identical configuration to neon. Given its larger size, the 3s2 di-electron is not as well-bound as the 2s2 di-electron on beryllium. Magnesium will therefore donate its valence electrons more readily than beryllium, but it will not be as reactive in doing so as the metals below it in Group II such as calcium, strontium, or barium.

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As we saw in the case of neon, the 2nd shell orbitals are more like spherical tetrahedra, and the 3rd shell is a di-electron in a spherical s-orbital. These orbitals represent phase-locked, resonant, coherent, harmonic, stationary waves.

Magnesium has a smaller atomic radius than sodium. (This square represents the size of the largest atom). The decrease in size, as we move across the third row of the periodic table, results from an increase in effective nuclear charge.

Its electronegativity value makes it a metal, though slightly less metallic than sodium. This is because its stronger effective nuclear charge makes it hold its electrons more strongly.

Ion formation

Magnesium is more willing to lose its two valence electrons in an ionic interaction than is beryllium because it is larger, and it will lose both at the same time in order to reach the stability of a full 2nd shell. This is the same electron configuration as the 2s22p6 noble gas configuration of neon — a multi-di-electron state with two concentric full shells. That is why magnesium forms a 2+ ionic state.

Neutral magnesium (Mg) atom (L) compared to the much smaller Mg2+ ion (R)

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OTHER GROUP II ELEMENTS: Beryllium, Magnesium, Calcium, Strontium, Barium